Comparative study of repeat breeds and healthy mares through endometrial Comparative study of repeat breeds and healthy mares through endometrial Comparative study of repeat breeds and healthy mares through endometrial Comparative study of repeat breeds and healthy mares through endometrial Comparative study of repeat breeds and healthy mares through endometrial histology and plasmatic progesterone concentrations histology and plasmatic progesterone concentrations histology and plasmatic progesterone concentrations histology and plasmatic progesterone concentrations histology and plasmatic progesterone concentrations.] Estudo comparativo de éguas repetidoras ou não de cio através da avaliação histológica do endométrio e das concentrações plasmáticas de progesterona. Pesquisa Veterinária Brasileira 27 (12) The study aimed to compare endometrial histology and plasmatic progesterone (P4) concentration of repeat breeds and healthy mares. The hypothesis was that there is a correlation between infertility and endometrial histology and P4 concentration in both groups. A total of 36 Campolina and Mangalarga Marchador mares in reproductive age (3-23 years) were used, 11 of them were healthy mares (Control group, 7 embryo recipient and 4 embryo donors), and 25 repeat breeders (10 embryo recipient and 15 embryo donors), classified as based on their reproductive history. Endometrial and blood samples were collected for respectively histological and plasma progesterone concentration evaluation. The endometrial samples obtained after biopsy were fixed in Bouin's fluid, processed, included in paraffin, and stained with HematoxylinEosin (HE) for histopathological examination. Plasmatic progesterone concentrations were evaluated by enzyme immunoessay (ELISA). There was no correlation between progesterone concentration and fertility. But there was a positive correlation between age and fertility, as older mares had major tendency of subfertility than younger ones. There was also a correlation between biopsy categories and fertility, as more histological alterations were found, higher were the chances for the mares to be subfertile. However not all mares classified as Category I and II maintained pregnancy until parturition. Other factors could influence pregnancy maintenance. In the same way, not all mares in Category III were infertile. The endometrial biopsy was shown to be an easy and cheap diagnostic technique with minimal discomfort to the animals and, together with other data, to be a very important component in the investigation of mare fertility.

The aim of this study was to analyze through histomorphometry, epithelial structures of the mare's endometrium classified according to Kenney and Doig (1986). Histomorphometric analysis of the luminal and glandular epithelial cell heights, glandular lumen diameter, glandular density, percentage of glands with apparent lumen and with intraluminal secretion, and a descriptive analysis of the endometrium was made in 65 endometrial biopsies. Samples were collected during estrus (n=30) and diestrus (n=35), fixed in Bouin's solution, embedded in paraffin HxE and classified according to Kenney and Doig (1986) categories. Groups of IIa category obtained the greatest medium cell heights for luminal and glandular epithelium, and groups of III category obtained the smallest values, during estrus and diestrus. The medium heights of luminal epithelium, glandular epithelium and glandular lumen diameter of samples collected during estrus were greater than those collected during diestrus. The gland density was greater during diestrus than estrus. This work showed that histomorphometry could improve the consistency in biopsy evaluation by furnishing objective data.